WO2020112819A1 - Protection contre la corrosion par gaz inerte élevée dans des systèmes de refroidisseur d'eau en boucle fermée - Google Patents

Protection contre la corrosion par gaz inerte élevée dans des systèmes de refroidisseur d'eau en boucle fermée Download PDF

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Publication number
WO2020112819A1
WO2020112819A1 PCT/US2019/063315 US2019063315W WO2020112819A1 WO 2020112819 A1 WO2020112819 A1 WO 2020112819A1 US 2019063315 W US2019063315 W US 2019063315W WO 2020112819 A1 WO2020112819 A1 WO 2020112819A1
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Prior art keywords
pipe network
inert gas
water
oxygen
vent
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PCT/US2019/063315
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English (en)
Inventor
Jeffrey T. KOCHELEK
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Engineered Corrosion Solutions, Llc
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Application filed by Engineered Corrosion Solutions, Llc filed Critical Engineered Corrosion Solutions, Llc
Publication of WO2020112819A1 publication Critical patent/WO2020112819A1/fr

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F5/00—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
    • F24D17/00—Domestic hot-water supply systems
    • F24D17/02—Domestic hot-water supply systems using heat pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
    • F24D19/00—Details
    • F24D19/0092—Devices for preventing or removing corrosion, slime or scale
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F5/00—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater
    • F24F5/0007—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater cooling apparatus specially adapted for use in air-conditioning
    • F24F5/0014—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater cooling apparatus specially adapted for use in air-conditioning using absorption or desorption
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2339/00—Details of evaporators; Details of condensers
    • F25B2339/04—Details of condensers
    • F25B2339/047—Water-cooled condensers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B25/00—Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00
    • F25B25/005—Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00 using primary and secondary systems

Definitions

  • a chiller system removes heat from a liquid via a vapor-compression or absorption refrigeration cycle. This liquid can then be circulated through a heat exchanger to cool equipment, or another process stream (such as air or process water). As a necessary by product, refrigeration creates waste heat that must be exhausted.
  • the basic components of most water chiller systems include a compressor that converts energy into compressed refrigerant.
  • Compressed refrigerant is transferred to a condenser that transfers heat from the refrigerant to a water coolant.
  • the compressed refrigerant changes state from a gas to a liquid in the condenser and then travels to an evaporator where it is allowed to expand in the evaporator.
  • the expansion of the high pressure liquid refrigeration reduces the temperature of the evaporator.
  • the liquid to be cooled is pumped through the evaporator heat exchanger and heat is transferred to the refrigerant.
  • the low pressure vapor is carried back to the compressor and the cycle begins again for the refrigerant.
  • the coolant flows from the evaporator heat exchanger to the load where the heat is transferred to the coolant in the load heat exchanger and then returns back to the evaporator to repeat the cycle.
  • Chiller systems may be placed into service in large scale facilities to provide conditioned air for distribution in one or more portions of the facility. Chiller systems are
  • DocID: 4811-3835-7421.2 1 also utilized in industrial process applications and integrated into process or laboratory equipment to cool products or machinery. They are widely used in connection with molding, metal working, welding, die-casting, machine tooling, chemical processing, and other industries, as well as to provide cooling for high heat generating specialized equipment. Water-based chiller units are a common choice in industrial process applications.
  • chiller systems operate by distributing chilled water to various heat exchanging structures, which cool air within the space associated with the heat exchanger by heat transfer. The heated water is then recirculated to the chiller to be recooled.
  • water chiller systems typically include a separate condenser water loop and are connected to exterior cooling towers to improve thermodynamic performance and may provide increased efficiency versus air-cooled and evaporatively cooled chiller systems.
  • These systems are typically installed as closed- loop systems, including the chiller unit, condenser, and pump station with recirculating pump, expansion valve, no-flow shutdown, and internal cold water control.
  • An internal tank helps maintain cold water temperature and prevents temperature spikes from occurring.
  • Closed- loop industrial water chillers recirculate clean water at a constant temperature and pressure to increase the stability and reproducibility of water-cooled machines and instruments.
  • water chiller systems utilize carbon steel - also referenced as black steel - piping or similar ferrous or cuprous materials.
  • Oxygen that is trapped within the pipe network reacts with the steel piping to cause corrosion thereby causing multiple negative results, including pitting pipe surfaces and corrosion by product debris (iron oxide hematite) that is then trapped within the closed system.
  • product debris iron oxide hematite
  • deterioration and corrosion of piping in closed-loop water chiller systems can involve several factors.
  • Second, depletion of biocide or other chemicals used to treat the water in the system in an attempt to control corrosion in the system due to the presence of tuberculation, organic matter, and microbiological organisms associated therewith may result in microbiological growth.
  • leaks can result from general corrosion and/or microbiologically influenced corrosion, such as oxidation by trapped air.
  • Microbiological influenced or induced corrosion can result when waterborne or airborne microbiological organisms, such as bacteria, molds, and fungi, are brought into the piping network of the protection system with untreated water and feed on nutrients within the piping system. Over time, the biological activities of these organisms can cause significant problems within the piping network. Both ferrous metal and cuprous metal pipes may suffer pitting corrosion leading to pin-hole leaks. Iron oxidizing bacteria form tubercles, which can grow to occlude the pipes. Tubercles may also break free from the pipe wall and accumulate in particularly sensitives areas, such as in or near heat exchangers. Even
  • An aspect of the present disclosure is to provide a closed loop water chiller system and method of operating a closed loop water chiller system.
  • An inert gas source such as nitrogen gas source is connected with the pipe network. Inert gas is supplied from the inert gas source to the pipe network. In certain aspects, the inert gas is supplied to the inert gas while the pipe network is filled with water. In another aspect, the inert gas is supplied to the pipe network while the pipe network is being drained of water. In yet another aspect, the inert gas is supplied to the pipe network while the pipe network is being filled with water.
  • Gas may be discharged from the pipe network after supplying inert gas and prior to filling the system with water.
  • the supplying and discharging of inert gas from the inert gas source to the pipe network may be repeated before supplying water to the pipe network, thereby increasing concentration of inert gas in the pipe network or during draining of water from the pipe network to minimize oxygen from entering the pipe network.
  • a venting assembly may be provided that is operable to vent air under particular circumstances, such as pressure in the pipe network being above a particular pressure level.
  • the pressure level may be fixed or adjustable.
  • a gauge may be provided for setting an adjustable pressure level.
  • the venting assembly may include an air vent and an airflow regulator.
  • the air vent is connected with the pipe network and discharges to the airflow regulator.
  • the air vent may further include a redundant air vent, with the air vent discharging to the airflow regulator through the redundant air vent.
  • the airflow regulator may be in the form of a pressure relief valve, a back-pressure regulator, or a check valve.
  • a sampling port may be provided for sampling air that is discharged from the airflow regulator.
  • an inline corrosion monitor may be incorporated into the system.
  • FIG. 1 is a schematic drawing of a first exemplary closed loop water chiller system as is known in the art.
  • FIG. 2 is a schematic drawing of a second exemplary closed loop water chiller system as is known in the art.
  • FIG. 3 is a schematic drawing of a first embodiment of a closed loop water chiller system incorporating an inert gas source in the water loop on the evaporator side of the chiller unit as described herein.
  • FIG. 4 is a schematic drawing of another embodiment of a closed loop water chiller system incorporating an inert gas source and vent in the water loop on the evaporator side of the chiller unit as described herein.
  • FIG. 5 is a schematic drawing of a yet another embodiment of a closed loop water chiller system incorporating an inert gas source, vent and inline corrosion detector in the water loop on the evaporator side of the chiller unit as described herein.
  • FIG. 6 is a front elevation of an exemplary venting assembly suitable for use in embodiments of the present disclosure
  • Fig. 7 is a flow diagram of an exemplary inerting process according to an embodiment of the present disclosure.
  • Fig. 8 is a flow diagram of an exemplary drain and refill process according to an embodiment of the present disclosure.
  • compositional percentages are by weight of the total composition, unless otherwise specified.
  • the word“include,” and its variants is intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that may also be useful in the materials, compositions, devices, and methods of this technology.
  • the terms“can” and“may” and their variants are intended to be non-limiting, such that recitation that an embodiment can or may comprise certain elements or features does not exclude other embodiments of the present technology that do not contain those elements or features.
  • “A” and“an” as used herein indicate“at least one” of the item is present; a plurality of such items may be present, when possible.“About” when applied to values indicates that the calculation or the measurement allows some slight imprecision in the value (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If, for some reason, the imprecision provided by“about” is not otherwise understood in the art with this ordinary meaning, then“about” as used herein indicates at least variations that may arise from ordinary methods of measuring or using such parameters. In addition, disclosure of ranges includes disclosure of all distinct values and further divided ranges within the entire range. [0033] There are several factors that can affect corrosion of a closed loop water chiller system.
  • the source water may include biological contaminants, dissolved and/or solid nonbiological contaminants, trapped air, and dissolved gases.
  • the system is in constant contact with liquid water.
  • the corrosion process permits or accelerates further corrosion; for example, the corrosion byproduct (e.g. iron oxide) may be shed, sloughing off to expose new metal (e.g., iron) to oxidation.
  • the corrosion byproduct e.g. iron oxide
  • new metal e.g., iron
  • Pipe materials typically come from the manufacturer or distributor with all of the associated open-air corrosion on the internal and external walls. This can include but is not limited to: iron oxide mill scale caused during the manufacturing process by condensation of water on the metal surfaces and the subsequent generalized oxygen corrosion that results from oxygen attack, the metal loss is typically minimal with no significant pitting; debris from the storage yard on the threads and in the ends of the pipe; and the presence of other solids associated with outside storage, such as spider webs, dead bugs, etc.
  • additional sources of debris and fouling may end up inside the assembled network of piping, including: residual cutting oil from the thread cutting process during installation; metal filings from the thread cutting process during installation; various forms of hydrocarbon based thread lubricants; and Teflon® tape used in assembly of the pipe fittings.
  • the source water used in the systems is generally from a fresh potable water source with very low total dissolved solids (TDS).
  • TDS total dissolved solids
  • the water is generally saturated with oxygen from the atmosphere and contains very little, if any, insoluble suspended solids. It may also contain small (less than about 2 ppm) amounts of residual chlorine from municipal treatment at the source.
  • the water may not contain any detectable levels of microorganisms, however, this does not preclude the presence of microorganisms, as they will simply be difficult to detect at the low levels that exist in the potable water.
  • the pipe network is filled and charged with water.
  • all of the debris that is clinging to the interior walls will become mobilized.
  • Materials that are insoluble in water will generally sink to settle and collect in all of the low spots within the system due to gravity.
  • the solids will collect at the six o'clock position, when viewing a pipe in cross-section.
  • Any hydrocarbon within the system will float on the water and will tend to agglomerate (i.e., oil wet) any insoluble particulates that are contacted. It is also difficult to completely remove all of the air during the water charging process. Whatever air is left in the system creates pockets within the pipes and results in a discrete air/water interface. As the system is pressurized, air will also dissolve into the water and quickly reach a state of equilibrium.
  • Oxygen corrosion may be the predominant form of corrosion and metal loss within the system. Air contains approximately 21% oxygen, and unless the source water is mechanically deaerated to effect oxygen removal, it will generally contain about 8-10 ppm of dissolved oxygen when it first enters the piping. The oxygen will immediately react with any free iron it contacts on the pipe walls according to the following equations:
  • the initial fill of water will remove iron from the pipe walls and some small level of metal loss will occur.
  • the metal loss will be most acute at the air/water interface where the dissolved oxygen content will be the highest.
  • the soluble iron that is liberated from the pipe walls at the interface will almost immediately precipitate as iron oxide, probably as ferric oxide, commonly known as rust.
  • the iron oxide may adhere to the pipe wall for a time, just below the air/water interface, but because of the loose, non-adhesive nature of the deposit, it is highly likely that the iron oxide will slough off and settle to the bottom of the pipe.
  • the flow of water in the pipe network will cause the deposits to be shed, exposing new free iron for attack by oxygen. The oxygen will be consumed and corrosion will slow down. If left undisturbed, the system could remain at a low general corrosion rate for a long period of time.
  • MIC microbiologically influenced corrosion
  • microorganisms can act to influence corrosion in three different ways.
  • microorganisms can produce slimes and deposits that accelerate the underdeposit corrosion mechanisms; e.g., oxygen concentration cells in aerobic environments.
  • microorganisms produce metabolic by-products that directly contribute to the corrosion reaction; e.g., organic acid producers that solubilize the iron in mild steel.
  • microorganisms produce metabolic by-products that indirectly contribute to the corrosion reaction by acting as a cathodic depolarizer; e.g., sulfides produced by sulfate-reducing bacteria.
  • Acid Producing Bacteria are a variety of heterotrophic anaerobic bacteria that share the common ability to produce weak organic acids. As they produce acids, APB cause the pH under the deposit to drop significantly from neutral to acidic with a terminal pH of about 3.5 to about 5.5. These acidic conditions (up to 1000 times more acidic than the source water) are very corrosive and will cause significant metal loss in ferrous metal or cuprous metal components. Because these acid-producing activities occur under anaerobic conditions, APB can exist as partners in corrosion with sulfate reducing bacteria.
  • Sulfate-Reducing Bacteria are a group of anaerobic bacteria that generate hydrogen sulfide (3 ⁇ 4S) as a metabolic by-product of the reduction of sulfate in the water or from a mineral scale deposit.
  • Hydrogen sulfide is a colorless, toxic and flammable gas that is characterized by the typical rotten egg odor which is detectable by humans at about 0.005 ppm in the air. Concentrations of hydrogen sulfide in the air above 800 ppm are lethal to humans.
  • the sulfide anion reacts spontaneously to produce iron sulfide, a finely divided black crystal, which can manifest itself as“black water”.
  • SRB are difficult to detect because they are anaerobic and tend to grow deep within biofilms (slimes) as a part of a mixed microbial community. SRB may not be detectable in the free- flowing water over the site of the fouling.
  • Heterotrophic Aerobic Bacteria use oxygen to respire as part of their metabolism. They pose problems in piping networks by contributing to slime formations on the pipe walls. As the slimes accumulate solids from the system, conditions are created that favor the acceleration of under-deposit corrosion mechanisms.
  • Iron-Related Bacteria are typically divided into two sub-groups e.g., iron-oxidizing and iron-reducing bacteria. IRB use iron in their metabolism to create red colored slimes,“red water” and can produce odor problems in piping. These bacteria function under different reduction-oxidation (redox) conditions and use a variety of nutrients for growth.
  • redox reduction-oxidation
  • Slime Forming Bacteria are able to produce large amounts of slime without necessarily having to use any iron. Iron bacteria also produce slime but usually it is thinner and involves the accumulation of various forms of iron. Slime-forming bacteria generally produce the thickest slime formations under aerobic (oxidative) conditions.
  • the corrosion rate in the system can be accelerated by the following mechanisms: (1) slime formation— under-deposit pitting corrosion; (2) acid production— acidic pitting corrosion; and (3) sulfide anion production— cathodic depolarization resulting in pitting corrosion. [0048] Mechanical deposit removal can allow additional corrosion. Anytime a corrosion deposit is removed from the metal surface, it creates a new site for attack. This will most often occur at the air/water interface and repeated removal of the deposit will create crevices.
  • Draining and refilling the system also allows additional corrosion.
  • the high rate of oxygen corrosion that exists with a fresh supply of air will remove a new layer of iron from the pipe walls. Any deposits that exist on the metal surfaces will become oxygen concentration cells in the new oxygen rich fluids and the otherwise low general rate of corrosion will be greatly accelerated and pitting will occur.
  • the present technology includes closed loop water chiller systems and methods of reducing corrosion in closed loop water chiller systems.
  • a closed loop water chiller system 10 includes an evaporator side water pipe network 12, a condenser side water pipe network 14, a compressor 20, a condenser 22, an evaporator 24, and an inert gas source 26 connected with at least one of the water pipe networks 12, 14.
  • the inert gas source 26 may be, for example, a nitrogen generator, a tank of compressed combination, or a combination of the two.
  • the nitrogen generator may be a nitrogen membrane system or a nitrogen pressure swing adsorption system.
  • the present systems and methods reduce or nearly eliminate corrosion that typically affects conventional closed loop water chiller systems, which can deteriorate or even compromise function.
  • Either or both of the evaporator side water loop 12 and/or the condenser side water loop 14 may be provided with embodiments of the inerting system described herein. Further in some embodiments of the present disclosure, a single gas source 26 may service both of the pipe networks 12, 14.
  • the nitrogen generator 26 can provide nitrogen on-demand to fill and/or purge the pipe network(s) 12 and/or 14 as desired.
  • the generator 26 may operate in conjunction with a sensor 31, such as an oxygen sensor, to operate automatically on a periodic basis, or on a continuous basis.
  • the nitrogen generator 26 is capable of generating a stream of gas having a greater concentration of nitrogen than air, where air is about 78% nitrogen.
  • the nitrogen generator may produce a stream of at least 85%, at least 90%, at least 95%, or at least 99% nitrogen.
  • the nitrogen produced by the nitrogen generator 26 may be supplied to displace oxygen to below detectable limits in the pipe network(s), 12 and/or 14, or to displace oxygen below a particular threshold within the pipe network(s) 12 and/or 14.
  • oxygen may be displaced to where it is less than 20 ppm, less than 15 ppm, less than 10 ppm, less than 5 ppm, or less than 1 ppm.
  • Nitrogen generators include nitrogen membrane systems and nitrogen pressure swing adsorption systems.
  • a membrane nitrogen generator is a modular system consisting of pre-filtration, separation, and distribution sections. Controls for the system are included in the nitrogen separation unit.
  • Ambient air enters the feed air compressor, which may be an oil injected rotary screw air compressor, via its inlet filter. Air is compressed and travels through an aftercooler and, in many systems, a refrigerated air dryer.
  • the filtration system which utilizes a combination of particulate, coalescing, and carbon adsorption technologies.
  • the filters are fitted with automatic condensate drains.
  • Units may be fitted with an air circulation heater and controls, which is installed in the air stream before the nitrogen membrane(s), but after the final filter and pressure regulator. The heater maintains a constant temperature of compressed air to the membranes, enhancing stability and performance.
  • the nitrogen membrane module(s) are located in the heated air stream. On lower purity systems, such as 99% N2 and below, the membranes are connected in parallel. On higher purity systems, such as 99% N2 or higher, the membranes may be connected in series or using a combination of series and parallel. Slowing down the flow through the membrane separators will automatically give higher nitrogen purity as well. High purity systems have separate permeate connections. One is strictly waste gas, but the second one is a line that can be re-circulated back to the feed compressor intake to enhance purity and productivity. After the air passes through the membrane bundle(s), it is essentially nitrogen plus trace amounts of inert gasses and the specified oxygen content. A built-in flow meter may be installed to constantly monitor nitrogen flow. The nitrogen membrane module(s) may be operated at ambient temperatures as well to eliminate the need for electricity. Operation at reduced temperatures may yield lower productivity or reduced nitrogen purity.
  • adsorption technology is a physical separation process, which uses the different adsorption affinities of gases to a microporous solid substance, the so-called adsorbent.
  • Oxygen for example, has a higher adsorption capacity or quicker adsorption time to some carbon molecular sieves compared to nitrogen. This characteristic is used within the PSA process for the generation of nitrogen from air.
  • the main advantages of this process are the ambient working temperature, which results in low stresses to equipment and adsorbent material, and the low specific power consumption.
  • the PSA-nitrogen generator typically includes the main equipment: air compressor, refrigerant dryer, air receiver tank, two adsorber vessels filled with adsorbent material and a product buffer. Each adsorber operates on an alternating cycle of adsorption and regeneration resulting in a continuous nitrogen product flow. PSA-nitrogen generators may be designed with just one adsorber vessel as well in order to simplify the design.
  • the PSA-nitrogen generator works according to the following process steps.
  • First is an adsorption step, where compressed and dried air at ambient temperature is fed into the PSA-vessel (adsorber) at the compressor discharge pressure.
  • the adsorber is filled with molecular sieves.
  • the remaining moisture and carbon dioxide in the air are removed at lower layers of the bed and oxygen is adsorbed by the upper molecular sieve filling.
  • the remaining, nitrogen-rich product gas leaves the adsorber at the outlet and is fed to the nitrogen buffer.
  • the adsorption process is interrupted so that no oxygen can break through at the adsorber outlet.
  • Second is a regeneration ⁇ purge step, where the saturated adsorber is regenerated by means of depressurization and additionally by purging with nitrogen produced by the second adsorber in order to remove the adsorbed gases H2O, CO2, and Ch from the adsorbent bed. The waste gas is vented to the atmosphere.
  • Third is a re-pressurization step, where after regeneration the adsorber is refilled with air and part of the recycled nitrogen. The adsorber is then ready for the next adsorption step.
  • Suitable nitrogen generators include those available from: Generon IGS (Houston, Tex.), manufacturer of membrane and PSA nitrogen generators; Ingersoll Rand (Montvale, N.J.), manufacturer of membrane and PSA nitrogen generators; On Site Gas (Newington, Conn.), manufacturer of nitrogen and oxygen generators; South Tel Systems (Raleigh, N.C.), manufacturer of nitrogen generators; and Air Products (Allentown, Pa.), manufacturers of nitrogen generators.
  • Corrosion in the pipe network(s) 12 and/or 14 is reduced by displacing oxygen within the piping using an inert gas that does not react with the pipe material, for example, nitrogen, from the inert gas source.
  • Displacing oxygen with nitrogen includes filling the pipe network(s) 12 and/or 14 with pressurized inert gas from the inert gas source 26. The pressurized inert gas thereby displaces air, which contains about 21% oxygen, out of the piping.
  • Displacing oxygen with inert gas can also include filling the pipe network(s) 12 and/or 14 with water and providing inert gas into the water as it fills or is contained in the pipe network(s) 12 and/or 14.
  • the inert gas added to the water thereby forces dissolved oxygen out of the water into the gas phase which can be vented out of the pipe network(s) 12 and/or 14 through vents 28 that are specifically designed to remove the trapped gasses from the pipe network(s) 12 and/or 14.
  • vents 28 that are specifically designed to remove the trapped gasses from the pipe network(s) 12 and/or 14.
  • the present systems and methods use an inert gas, for example, nitrogen, to fill any void in the pipe network(s) 12 and/or 14 of the water chiller system and to mitigate the corrosion of ferrous and cuprous metal components.
  • the inert gas is used to purge the initial quantities of inert gas and other gases trapped in the pipe network(s) 12 and/or 14 through one or more vent points 28 in the pipe network(s) 12 and/or 14, and to allow the quantity of inert gas in the piping to increase and ultimately approach about 95% or more in preferred embodiments.
  • the inert gas source 26 may be used to purge or recharge the pipe network(s) 12 and/or 14 with inert gas.
  • the nitrogen generator or other inert gas source 26 may be used to recharge the pipe network(s) 12 and/or 14 as needed and may be configured to do so automatically.
  • the system may also be configured to continuously supply pressurized nitrogen into the piping network using the nitrogen generator.
  • the nitrogen generator 26 provides a steady stream of pressurized nitrogen into the pipe network(s) 12 and/or 14.
  • the system may include a vent 28 such as a relief valve in order to control or limit the pressure in the pipe network 12.
  • the relief valve allows pressurized nitrogen to escape at a preset or adjustable limit to prevent over-pressurization.
  • Continuous venting of the pipe network/ s) 12 and/or 14 using one or more vents 28 or valves facilitates removal of any oxygen within the pipe network(s) 12 and/or 14 while maintaining a desired system pressure, if applicable.
  • the nitrogen generator 26 may alternately be used to provide additional water containing dissolved nitrogen in order to purge or recharge the pipe network(s) 12 and/or 14.
  • oxygen from the air may over time penetrate the pipe network(s) 12 and/or 14 through leaks in the system. Oxygen from the air may enter pockets of gas trapped within the pipe network(s) 12 and/or 14 and/or may dissolve into the water contained within the pipe network(s) 12 and/or 14.
  • the water can be sparged and vented by bubbling nitrogen through the water in order to strip the oxygen out of the water to a concentration below 5.0 ppm and, with adequate sparging time, below 1.0 ppm. At this level, oxygen corrosion of ferrous metal of cuprous metal components will be very minimal.
  • the nitrogen generator 26 may be used to provide nitrogen to the pipe network(s) 12 and/or 14 as needed, periodically, or continuously.
  • nitrogen may be bubbled through the pipe network(s) 12 and/or 14 to displace oxygen where nitrogen and the displaced oxygen are allowed to exit through vent 28.
  • the vent 28 is operable and positioned to retain the pressurized water within the pipe network but allows gas to exit.
  • the vent 28 may include a filter or membrane that is gas permeable but liquid impermeable.
  • the pipe network(s) 12 and/or 14 may be drained of water at various times for maintenance or other reasons.
  • inert gas may be supplied to the pipe network(s) 12 and/or 14 in order to minimize or eliminate air and oxygen from reentering the pipe network(s) 12 and/or 14.
  • oxygen is again displaced with inert gas by introducing pressurized inert gas into the pipe network(s) 12 and/or 14 and/or filling the pipe network(s) 12 and/or 14 with water and providing inert gas into the water as it fills and/or while it is contained in the pipe network(s) 12 and/or 14.
  • vents 28 may be incorporated into the system. Venting assemblies, including manually operated, electrically operated, and redundant vents, and methods of venting piping networks, suitable for use in chiller systems as described herein are described in U.S. Patent No. 8,636,023, issued January 28, 2014, U.S. Patent No. 9,717,935, issued August 1, 2017, and U.S. Patent No.9, 884, 216, issued February 6,2018, the entire disclosures of each of which are hereby expressly incorporated by reference. Due to the increased complexity of the piping networks in chiller systems, which may include multilevel arrangements in some applications, it may be advantageous to incorporate multiple vents 28 at various high points of the piping network to further facilitate venting of the network.
  • vents 28 provide for exhausting trapped air and oxygen during the inerting process.
  • the vents 28 prevent ingress of oxygen-containing air during draining or filling of the pipe network(s) 12 and/or 14.
  • pressurized inert gas may be allowed to exit the pipe network(s) 12 and/or 14 to prevent over pressurizing the network.
  • vent 32 is connected with pipe network 12.
  • the vent 32 does not always need to be the highest point in the pipe network(s) 12 and/or 14.
  • vent 32 is made up of an air vent 34 and an airflow regulator 35.
  • Air vent 34 discharges to airflow regulator 35.
  • the airflow regulator 35 may be in the form of a back-pressure regulator 36.
  • Back-pressure regulator 36 responds to the pressure in the pipe network(s) 12 and/or 14 by discharging air through air vent 34 that is above a set point pressure of the back-pressure regulator 36.
  • back-pressure regulator 36 may include a pressure gauge 37 that displays the pressure supplied to the back-pressure regulator 36 and an adjustment knob 38 that allows the set point to be adjusted.
  • a sample port 40 may be provided at back-pressure regulator 36 to allow the relative oxygen concentration (and, therefore, the nitrogen concentration) to be measured, Sample port 40 may be connected with a narrow gauge metal or plastic tube 42 to a port 44.
  • Vent 32 may further include a redundant air vent 46 that provides redundant operation in case of failure of primary air vent 34. Such redundancy avoids water from being discharged to back-pressure regulator 36 and to the environment upon failure of the primary air vent where it may cause damage before the failure is discovered.
  • primary air vent 34 may discharge to redundant air valve 46 which, in turn, discharges to back pressure regulator 36.
  • the primary air vent 34 and/or the redundant air vent 46 may comprise a float 33.
  • the primary air vent 34 and redundant air vent 46 if present, may have an identical configuration.
  • airflow regulator 35 can be made up of a pressure relief valve.
  • a pressure relief valve functions in a similar manner to a back-pressure regulator, except that its set point is fixed at the factory and cannot be field adjusted.
  • the airflow regulator can be in the form of a check valve which allows air to be discharged from air vent 34 to atmosphere, but prevents high oxygen content atmospheric air from being drawn through air vent 34 when the pipe network is drained of water.
  • Back-pressure regulator 36 and the alternative pressure relief valve are commercially available from multiple sources, such as Norgren Company of Littleton, Colo., USA.
  • Airflow regulator 35 operates by allowing air vented by air vent 34 to be discharged to atmosphere. However, airflow regulator 35 prevents atmospheric air, which is oxygen rich, from flowing through air vent 34 into the pipe network(s) 12 and/or 14, such as when it is being drained. In the illustrated embodiment in which airflow regulator 35 is made up of a back-pressure regulator or a pressure relief valve, airflow regulator 35 functions by opening above a set point pressure and closing below that set point pressure. Air vent 34 functions by opening in the presence of air alone (or other gaseous mixture) and closing in the presence of water.
  • vent 32 will be open to vent gas during filling of the pipe network(s) 12 and/or 14 with water which raises the pressure of the gas in the pipe network(s) 12 and/or 14 above the set point of the back-pressure regulator 36.
  • the presence of water at air vent 34 will close the air vent resulting in closing of the back-pressure regulator 36.
  • the pipe network(s) 12 and/or 14 is being emptied of water, the air pressure within the pipe network(s) 12 and/or 14 will decrease as a result of water being drained, as would be understood by the skilled artisan, thereby maintaining airflow regulator 35 closed to prevent drawing in a substantial amount of high oxygen content atmospheric air. This will prevent substantial amounts of oxygen rich atmospheric air from entering the pipe network(s) 12 and/or 14 during draining.
  • an inerting process 50 may be carried out with nitrogen or other inert gas as outlined in Fig. 7 for example.
  • Process 50 may start 52 with the technician setting 54 the set point pressure on back-pressure regulator 36.
  • Nitrogen source 20 is connected with the pipe network(s) 12 and/or 14 and nitrogen pressure is set 56.
  • the nitrogen pressure is set below the set point pressure of back-pressure regulator 36 to prevent back-pressure regulator 36 from opening during the inerting process 50.
  • a drain valve of the pipe network(s) 12 and/or 14 is closed and a nitrogen valve is opened to fill the pipe network(s) 12 and/or 14 with nitrogen rich air 58. The nitrogen valve is then closed to prevent additional gas injection.
  • the technician may then sample the relative concentration of oxygen and nitrogen at sample port 40 by opening port 44 and allowing air to flow through tube 42 for a sufficient time, such as several minutes, to allow levels to stabilize 60.
  • a manual or automatic oxygen meter can then be connected to port 44 to achieve continuous or intermittent oxygen readings.
  • Nitrogen concentration may be inferred at 60 by subtracting the oxygen concentration percentage from
  • a drain valve is opened 64. After a delay 66 to allow pressure in the pipe network(s) 12 and/or 14 to drop to atmospheric pressure, the drain valve is again closed and steps 58 through 62 repeated until it is determined at 62 that the concentration of nitrogen in the pipe network(s) 12 and/or 14 is high enough. It should be understood that steps 60 and 62 are optional and may be eliminated once process 50 has been performed one or more times. Once it is determined at 62 that the nitrogen concentration is sufficient, a water fill valve is then opened 68 to admit water to the pipe network(s) 12 and/or 14.
  • Water pressure in the pipe network may compress the nitrogen rich air in the pipe network(s) 12 and/or 14 to a fraction of its volume and raise the pressure of the air above the set point of back-pressure regulator 36. This causes back-pressure regulator 36 to discharge the nitrogen rich air until essentially all of the air is depleted from the pipe network(s) 12 and/or 14 at which time air vent 34 closes in the presence of water. Back-pressure regulator 36 then closes to prevent high oxygen rich air from entering the pipe network(s) 12 and/or 14 when it is subsequently drained of water.
  • the pipe network(s) 12 and/or 14 may be able to be drained and refilled using a drain and refill process 80 as shown in Fig. 8 without the need to repeat inerting process 50.
  • Drain and refill process 80 begins 82 with the pipe network(s) 12 and/or 14 filled with water either using inerting process 50 or by a conventional process.
  • Nitrogen source 26 is connected with the pipe network(s) 12 and/or 14 and the nitrogen pressure adjusted 84.
  • the nitrogen valve is opened 86 in order to allow nitrogen gas to flow into the pipe network(s) 12 and/or 14.
  • the drain valve is opened 88 to drain water from the pipe network(s) 12 and/or 14.
  • the concentration of nitrogen can be established at a desired level. For example, by choosing a nitrogen source of concentration between 98% and 99.9% and by filling and purging the piping network at approximately 50 PSIG for four (4) cycles, a concentration of nitrogen of between 97.8% and 99.7% can be theoretically achieved in the pipe network(s) 12 and/or 14. A fewer number of cycles will result in a lower concentration of nitrogen and vice versa.
  • a high nitrogen, or other inert gas system may be provided in certain embodiments without the need to apply a vacuum to the pipe network(s) 12 and/or 14 after draining in order to remove high oxygen air. This reduces the amount of time required to place the system back into operation after being taken down for maintenance. Also, the elimination of a vacuum on the pipe network(s) 12 and/or 14 avoids potential damage to valve seals, and the like.
  • inline corrosion monitoring systems and methods may be employed.
  • the inline corrosion monitoring system 30 and method may incorporate at least metal a coupon and an oxygen depletion area defined on a surface portion of the metal coupon as disclosed in U.S. Patent No. 8,893,813, issued November 25, 2014, the entire disclosure of which is hereby expressly incorporated by reference herein.
  • a mounting member positions the corrosion monitor assembly to be at least partially covered with water when the chiller system is in operation.
  • the oxygen depletion area may be defined by a non-metal material abutting the surface portion of the coupon.
  • the non-metal material may be a polymeric material, such as polytetrafluoroethylene (PTFE).
  • the corrosion monitor assembly may include another metal coupon and another oxygen depletion area defined on a surface portion of the other coupon.
  • the oxygen depletion area on the surface portion of the other coupon may be defined by a non-metal material abutting said surface portion of the other coupon. Opposite sides of a common non-metal material may abut the surface portions of the coupon and the other coupon.
  • the coupon and the other coupon may be made from metals that are the same or from different metals.
  • the metals may be chosen from galvanized steel, copper, brass, austenitic steel and mild steel.
  • the mounting member preferably positions the corrosion monitor assembly to extend across at least half of a diameter of the pip network.
  • a piping network of a chiller system includes a pipe having a first pipe portion and a second pipe portion.
  • the first pipe portion includes a wall having a first wall thickness
  • the second pipe portion includes a wall having a second wall thickness that is greater than the first wall thickness.
  • the system further includes structure coupled to the pipe and defining a sealed chamber between the structure and the first pipe portion, and a sensor for sensing a pressure in the sealed chamber.
  • a corrosion monitoring device in another application, includes a pipe having opposite ends and a middle portion positioned between the opposite ends.
  • the opposite ends of the pipe each include a wall having a first wall thickness
  • the middle portion of the pipe includes a wall having a second wall thickness that is less than the first wall thickness.
  • the corrosion monitoring device further includes structure coupled to the pipe and defining a sealed chamber between the structure and the pipe, and a sensor for sensing a pressure in the sealed chamber.
  • a method of installing a corrosion monitoring device in a chiller system includes removing a section of the pipe from the piping network of a chiller system to create two pipe ends with a space between, positioning the corrosion monitoring device in the space, and coupling the corrosion monitoring device to the two pipe ends.
  • a chiller system in another application, includes a pipe having a first pipe portion and a second pipe portion.
  • the first pipe portion includes a wall having a first wall thickness
  • the second pipe portion includes a wall having a second wall thickness.
  • the system also includes structure coupled to the pipe and defining a sealed chamber between the structure and the first pipe portion, and a sensor for sensing a parameter associated with the sealed chamber.
  • a corrosion monitoring device for a chiller system includes a pipe having opposite ends and a middle portion positioned between the opposite ends.
  • the opposite ends of the pipe each include a wall having a first wall thickness
  • the middle portion of the pipe includes a wall having a second wall thickness.
  • the corrosion monitoring device further includes structure coupled to the pipe and defining a sealed chamber between the structure and the first pipe portion, and a sensor for sensing a parameter associated with the sealed chamber.
  • a method of monitoring corrosion within a chiller system having a pipe, and structure coupled to the pipe and defining a sealed chamber between the structure and the pipe includes sensing, with a pressure sensor, a pressure within the sealed chamber. The method also includes detecting a change in pressure within the sealed chamber, corresponding to a breach of a pipe wall of the sealed chamber. The method further includes generating a signal in response to detecting the change in pressure within the sealed chamber.
  • a method of monitoring corrosion within a chiller system having a pipe, and structure coupled to the pipe and defining a sealed chamber between the structure and the pipe includes sensing a parameter associated with the sealed chamber, and detecting a change in the parameter associated with the sealed chamber, corresponding to a breach of a pipe wall of the sealed chamber. The method also includes generating a signal in response to detecting the change in the parameter associated with the sealed chamber.
  • Embodiments of the present systems and methods may further employ one or more oxygen sensors 31.
  • the oxygen sensor may be used to detect oxygen within the system and trigger the nitrogen generator to purge or flush the system with nitrogen gas, with water and dissolved nitrogen gas, and/or to bubble nitrogen gas through water already within the system.
  • the oxygen sensor may be used to measure effective displacement of oxygen during the initial setup or installation of the system, following actuation or testing of the system, and/or for monitoring of the system while in service.
  • the oxygen sensor may be used to monitor the water within the piping network to ensure oxygen has been effectively displaced and reduced below a desired threshold or is no longer detectable.
  • the oxygen sensor may be used in an automated system to trigger the nitrogen generator to purge or flush the system or the system may be manually activated based on a reading provided by the oxygen sensor.
  • the oxygen sensor may be coupled to an alarm indicating that oxygen is present or at an undesirable level within the pipe network.
  • Suitable oxygen sensors include those provided by: GE Sensing— Panametrics (Billerica, Mass.), built in oxygen analyzers; Maxtec (Salt Lake City, Utah), handheld oxygen analyzers; and AMI (Huntington Beach, Calif.), built in oxygen analyzers.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)

Abstract

La présente invention concerne un système de refroidisseur d'eau en boucle fermée et un procédé de fonctionnement d'un système de refroidisseur d'eau en boucle fermée qui comprend un système de refroidisseur d'eau comportant un réseau de tuyaux. Une source de gaz inerte, telle qu'une source de gaz d'azote, est raccordée au réseau de tuyaux. Un gaz inerte est distribué depuis la source de gaz inerte vers le réseau de tuyaux. Dans certains aspects, le gaz inerte est distribué depuis la source de gaz inerte dans le réseau de tuyaux tandis que le réseau de tuyaux est rempli d'eau. Dans un autre aspect, le gaz inerte est distribué au réseau de tuyaux tandis que le réseau de tuyaux est vidangé de l'eau. Dans un autre aspect supplémentaire, le gaz inerte est distribué au réseau de tuyaux tandis que le réseau de tuyaux est rempli d'eau. Un évent peut être disposé pour évacuer le gaz du réseau de tuyaux afin de faciliter le processus d'inertage. Dans d'autres modes de réalisation, des capteurs d'oxygène et/ou des détecteurs de corrosion en ligne peuvent être incorporés dans le système.
PCT/US2019/063315 2018-11-27 2019-11-26 Protection contre la corrosion par gaz inerte élevée dans des systèmes de refroidisseur d'eau en boucle fermée WO2020112819A1 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10141817A (ja) * 1996-11-07 1998-05-29 Yazaki Corp 真空漏洩検知方法
JP3357940B2 (ja) * 1996-11-01 2002-12-16 株式会社大氣社 空調設備の密閉式配管防食方法および空調設備
US20090266095A1 (en) * 2005-09-27 2009-10-29 Marco Pruneri Refrigerated Preservation Unit, Particularly for Domestic Use
US8141620B1 (en) * 2007-02-26 2012-03-27 United States Thermoelectric Consortium (USTC) Method for conditioning a cooling loop of a heat exchange system
US9526933B2 (en) * 2008-09-15 2016-12-27 Engineered Corrosion Solutions, Llc High nitrogen and other inert gas anti-corrosion protection in wet pipe fire protection system

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3357940B2 (ja) * 1996-11-01 2002-12-16 株式会社大氣社 空調設備の密閉式配管防食方法および空調設備
JPH10141817A (ja) * 1996-11-07 1998-05-29 Yazaki Corp 真空漏洩検知方法
US20090266095A1 (en) * 2005-09-27 2009-10-29 Marco Pruneri Refrigerated Preservation Unit, Particularly for Domestic Use
US8141620B1 (en) * 2007-02-26 2012-03-27 United States Thermoelectric Consortium (USTC) Method for conditioning a cooling loop of a heat exchange system
US9526933B2 (en) * 2008-09-15 2016-12-27 Engineered Corrosion Solutions, Llc High nitrogen and other inert gas anti-corrosion protection in wet pipe fire protection system

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